1

Re-use your analysis and run an interaction model between your IV and the other covariate. Plot the interaction as a coefficient plot.
For the coefficient plot, you can stick to easystats.

2

The plot might be quite vivid and colorful. This one’s rather an open task: Try to make it more dim and more greyish or apply just another theme.
Remember, the plots are base on ggplot2. You could choose from one of ggplot2’s built-in themes here: https://ggplot2.tidyverse.org/reference/ggtheme.html. In another step, you could adjust the scale’s colour, e.g., with scale_colour_grey(). Be creative.

3

Plot the interaction effect as a prediction.
For this purpose, you need the plot_model() function from sjPlot.